Work vehicles can be equipped with backhoes for doing excavation work. A backhoe is provided with a pivotal boom which is attached to the vehicle by a swing frame. The swing frame is provided with a vertical pivot for pivoting the backhoe about a vertical axis relative to the vehicle. The boom of the backhoe is joined to the swing frame by a horizontal pivot and can be pivoted relative to the swing frame about a horizontal axis. A dipperstick is pivotally coupled to the boom. The positions of the swing frame relative to the vehicle, the boom relative to the swing frame, and the dipperstick relative to the boom are controlled by hydraulic cylinders. Typically, a bucket is pivotally attached to the end of the dipperstick remote from the boom. A hydraulic cylinder pivotally attached to the dipperstick is used to position the bucket relative to the dipperstick through a bucket linkage.
When a work vehicle equipped with a backhoe is travelling between work sites, the boom is locked to the swing frame in a transport position. In this position, the swing frame is also locked relative to the work vehicle. A boom lock is used for locking the boom to the swing frame. Various examples of a boom lock are disclosed in U.S. Pat. Nos. 4,260,321, 5,064,339, and 5,967,737.
Referring to FIG. 1, a portion of a conventional backhoe 100 is shown in which a conventional boom 104 is locked to a swing frame 110 by a conventional boom lock 116 in the transport position. As shown, a dipper 106 is coupled at one end to a bucket 108 and at the opposite end to the boom 104. In an operational mode, the boom 104, dipper 106, and bucket 108 can be manually controlled by a control system 102. The bucket 108, in particular, can be controlled by a hydraulic cylinder 112 and the dipper 106 can be controlled by a different hydraulic cylinder 114. In the transport position, the backhoe 100 is positioned on a ground surface 118. The dipper 106 and hydraulic cylinder 114 are connected at a horizontal coupling point 120. At an uppermost point 122 of the backhoe, which is above the horizontal pivot point 120, a transport height H can be defined between this uppermost point 122 and a ground surface 118 upon which the vehicle moves. The transport height H can vary for different backhoes, but the height for many conventional backhoes is greater than 4.0 meters. However, at least in some countries, new regulations require backhoes to have a transport height H less than 4.0 meters. In addition, the operator has to apply a significant force (over 113 N) to manipulate the conventional boom lock to engage and disengage the boom 104. For some operators, it can be difficult to engage and disengage the boom 104 for operation.
A need therefore exists to provide a backhoe having a boom and dipper configuration which has a transport height less than four meters. It is further desirable to reduce the transport height without changing the design of the boom or dipper. It is also desirable to reduce the force required by the operator to engage and disengage the boom lock and boom.